This invention relates to an apparatus for the crushing or grinding of fibrous material, in particular fibrous material wet or mixed with water, preferably chips, in particular to drum refiners, with an engine-driven rotor having a preferably horizontal rotary shaft and at least one, in particular at least two, surface(s), conveniently surfaces of revolution, in particular frustoconial surface(s) inclined to the rotor axis or extending approximately normally thereto and provided with crushing or grinding elements or grinding plates, with diameters increasing away from the at least one material feed advantageously directed approximately radially to the rotor axis or approximately tangentially to the rotor jacket or housing shell, as well as optionally, if at least two surfaces, in particular surfaces of revolution inclined to the rotor axis or extending approximately normally thereto and having comminuting elements or the like are provided, those with opposing inclination to the rotor axis and a housing receiving the rotor having corresponding inner wall(s) and opposing crushing or grinding elements or grinding plates arranged thereon, the grinding gaps inclined to the rotor axis advantageously being at least partially variable or adjustable between crushing or grinding elements or grinding plates or the like of the rotor jacket conveniently having surfaces of revolution in particular frustoconical surfaces, and corresponding opposing crushing or grinding elements or grinding plates or the like of the inner housing walls.
Refiners of various types are used for the production of wood pulps, for instance CTMP (chemical thermomechanical pulp), TMP (thermomechanical pulp) and RMP. The high mechanical energy applied causes the generation of high frictional forces in the grinding gap in the known refiners and the defibration of the wood. Large amounts of steam are generated and have to be discharged in the or counter to the direction of flow of the grinding stock.
This steam discharge has two disadvantages: the backflowing steam impedes the feeding of the chips to the refiner because of its large volume, which limits the throughput of the refiner. The pressure in the refiner housing is not freely selectable in order to discharge as much steam as possible in the flowing direction of the grinding stock. For a good utilization of the steam, however, the highest possible pressure is of advantage.
Efforts have therefore been made towards an advantageous discharge of the steam. It is known with two-disk refiners to discharge the steam at the start of the grinding gap. The disadvantage of this embodiment resides in the fact that the steam is not directly separated from the fibrous material in the area in which the main volume of the steam is generated, for the pressure in the actual grinding zone of the refiner is essentially higher than the pressure at the inlet of the chips. In the known method mentioned above, only steam of low tension is present. Since the outlet openings for the steam are slightly inclined towards the center of the axis, in order to separate the steam from the solids, pressure is lost on letting off steam in overcoming the centrifugal forces. As a result, the backflow of steam against the feeding of the chips or the like can only be effectively reduced if the steam is discharged at a very low pressure level, which makes the sensible utilization of the energy content essentially more difficult.
It is the object of the invention to discharge the steam generated during the grinding operation directly from the area of the grinding zone in which steam development is highest and the pressure is also highest. This is achieved according to the invention in an apparatus of the type initially described by providing channels or bores for the discharge of steam spaced from the at least one material feed extending in particular approximately radially to the rotor axis or approximately tangentially to the rotor jacket or housing shell on the crushing or grinding surfaces or grinding plates or the like and optionally on the jacket of the rotor carrying them, said channels or bores piercing the crushing or grinding surfaces or grinding plates or the like and optionally their supports and being provided in the working area of the crushing or grinding elements or grinding plates or the like provided on the surface, conveniently surfaces of revolution, in particular frustoconical surfaces, inclined to the rotor axis or extending approximately normally thereto, on the one hand, and emptying into channels or bores optionally provided in the bottom of said supports and extending approximately normally to said channels or bores, on the other hand, and conveniently being connected to cavities in the housing. This means that channels or bores lead away in the grinding zone from the site where most steam is generated and where the highest steam pressure prevails; it is particularly convenient if channels or bores extending approximately normally to the rotor axis pierce the crushing or grinding surfaces or grinding plates or the like and their support and empty into channels or bores extending approximately normally thereto provided in the bottom of said supports. This brings about a particularly effective discharge of the steam in refiners provided with an engine-driven rotor; the movement of material along the grinding surfaces or the like and the discharge of the steam in the direction of the housing cavities takes place in the same direction; this is enhanced by the rotating movement of the rotor, on the one hand, and by the conical working surfaces or the like widening towards the housing cavities, on the other hand, and the steam discharge channels emptying there as a result of the generated centrifugal forces. According to the embodiment known from DE-AS 23 23 442, the centrifugal forces in the grinding zone act counter to the material flow, this apparatus, by the way, being a disk mill in which the problems are of an entirely different nature. Particularly striking effects in steam discharge can be achieved if the rotor jacket and the corresponding inner housing wall(s) are conveniently formed as surfaces of revolution, in particular as frustoconical surface(s), with a diameter increasing away from the at least one material feed, if the material feed advantageously extends approximately radially to the rotor axis or approximately tangentially to the rotor jacket or housing shell is provided approximately in the center of said housing and the crushing or grinding surfaces or grinding plates or the like extend on the jacket of a drumshaped rotor and correspondingly on the inner housing wall in particular symmetrically, to both sides away from the material feed on the inclined surface, conveniently a surface of revolution, in particular frustoconical surface, with a diameter increasing away from the material feed, the latter enclosing an angle with the rotor axis open to both sides of the front faces of the rotor and crushing or grinding surfaces or grinding plates or the like extending approximately parallel to the rotor axis and in particular directly connected thereto are conveniently provided between the material feed and said crushing or grinding surfaces or grinding plates or the like with increasing diameter, and if the channels or bores pierce the grinding surfaces or grinding plates and optionally the rotor jacket carrying them within the area of the widening surfaces, conveniently surfaces of revolution, in particular frustoconical surfaces, namely, that said channels or bores extend, for instance, in or near the center from the grinding surface to its supports by piercing the grinding plates or the like and emptying into channels or bores in the bottom of the grinding plates or the like or in or at their support(s), said channels or bores being connected to cavities in the housing of the apparatus or refiner. A convenient practical embodiment according to the invention can be so arranged that the crushing or grinding surfaces or grinding plates or the like forming the grinding gaps extending parallel to the axis or extending approximately normally to the axis are arranged symmetrically to the median plane(s) of the, conveniently two or more, radial or tangential material feed(s) advantageously evenly distributed over the circumference of the rotor and steam discharge channels pierce the grinding surfaces or grinding plates or the like or the rotor jacket carrying them transversely to the rotor axis for instance in the area of more than two thirds to three quarters of the path of the grinding stock between the grinding surfaces or grinding plates or the like measured from the entry between said surfaces or plates to its exit into the housing cavities. A particularly effective practical embodiment is obtained if the crushing or grinding surfaces or grinding plates or the like parallel to the axis are followed by the, in particular frustoconical, crushing or grinding surfaces or grinding plates or the like, inclined at an angle of approximately 5 to 45 degrees, in particular 15 degrees, to the rotor axis and for instance the steam discharge channels or bores emptying into the inner grinding surfaces or grinding plates or the like and extending approximately normally to the rotor axis are located approximately in or near the center of said inclined surfaces and in corresponding places of the rotor jacket carrying them. A regulation of the grinding gaps and thus above all a control of the pulp quality and under certain circumstances of the steam control and steam supply may also prove advantageous. This may be achieved according to the invention by providing for the crushing or grinding surfaces or grinding plates or the like to be attached to at least one, conveniently two, supports displaceable or adjustable in the housing, in particular for the outer opposing crushing or grinding surfaces or grinding plates located opposite the mouths of the steam discharge or bores in the working area, to be attached to at least one stator ring, in particular to at least two stator rings which are preferably displaceable independently of one another.
The invention is advantageously applicable if an annular material feed gap connected to an annular space enclosing the outside of the rotor within the housing, into which space the approximately tangential or approximately radial material feed(s) empty, is provided approximately in the cross-axial median plane of the apparatus or its housing between the crushing or grinding surfaces parallel to the axis and thus between those inclined to the rotor axis and provided with steam outlets. For discharging the steam, it is convenient if cavities are provided in the area of the two front walls of the housing in the vicinity of the shaft bearings provided on both sides of the rotor having crushing or grinding surfaces parallel and inclined to the axis and optionally extending approximately normally to the axis, into which cavities the in particular conical or normally extending crushing or grinding gaps and their steam discharge channels or bores empty, said cavities being sealed steam-tight against the two bearings by the special sealing units inserted in the bearing housing between rotor and bearings on the rotor side and conveniently being provided with discharge openings for the comminuted material. A considerable saving in energy can be achieved in the operation of the apparatus according to the invention. If the drumshaped rotor provided on its jacket with crushing or grinding surfaces extending approximately parallel to its axis and on both sides adjacent crushing or grinding surfaces with diameters increasing away from the material feed and connected to steam discharges or provided therewith and optionally with crushing or grinding surfaces extending approximately normally to the rotor axis is supported in sliding bearings by means of the rotary shaft fixedly attached to it and a special starting engine, in particular a direct current engine, is provided for the starting operation and the main engine is designed for an operation at about 3,000 up to 3,600 rpm at full load.
The invention is particularly useful in drum refiners or the like with horizontal rotary axis. But under certain circumstances, it can also be applied advantageously if the rotary axis of the rotor extends vertically.
The invention also relates to a crushing or grinding element for drum refiners for the crushing or grinding of fibrous material with an engine-driven rotor, the element being attachable to the rotor shell, conveniently at least one surface of revolution inclined to the rotor axis or extending approximately normally thereto with a diameter increasing away from the material feed, and provided with crushing or grinding elements, optionally, if at least two surfaces of revolution inclined to the rotor axis or extending approximately normally thereto and having comminuting elements or the like are provided, some of them being of opposing inclination to the rotor axis, the grinding gaps inclined to the rotor axis between the crushing or grinding elements on inner housing walls being at least partially adjustable, with channels or bores for the discharge of steam spaced from the material feed piercing the crushing or grinding surfaces provided on the rotor shell and optionally their supports and the rotor shell itself, one end of said channels or bores being provided in the working areas of the crushing or grinding elements provided on the surfaces of revolution inclined to the rotor axis or extending approximately normally thereto and their other end emptying into channels or bores extending approximately normally to the steam discharge channels or steam discharge bores, and conveniently being connected to cavities in the housing. Crushing or grinding surfaces of this type are subject to wear. This is the case, for instance, when the crushing or grinding surfaces are formed conically. Such surfaces must be repeatedly replaced during the use of such drum refiners in order to assure an adequate crushing or grinding performance.
According to the invention, this object is achieved in a particularly convenient manner by providing for the crushing or grinding element(s) to be formed as cylinder segment(s) provided with anchoring projections of hammerhead-like cross section on the side facing the rotor axis and engageable in corresponding rotor grooves of hammerhead-like cross section, said cylinder segments serving for the discharge of steam.
Segments of this type have two main advantages: On the one hand, it is comparatively simple to slide them into and out of the corresponding rotor grooves, e.g. releasable wedges being used for firm anchoring. On the other hand, it is possible to exchange only individual areas of the crushing or grinding surfaces on the rotor shell and to leave the grinding surface portions of lesser wear with the remaining cylinder segments supporting them on the rotor for further use. In this way, the grinding performance is optimized at simultaneous economical use of the machine parts and additionally enhanced by the convenient steam discharge made possible at the same time.
The patterns of the crushing or grinding surfaces themselves can be formed in any given manner, as ribs, serrations, grooves and ribs or the like.
According to a further development of the invention, ribs of hammerhead-like cross section and contacting two each adjacent segments may be provided on the rotor shell for retaining the cylinder segment(s). A particularly secure seat of the cylinder segments during operation can be achieved if the transition surfaces between the hammer heads and the hammer head stems are planes of which each forms an identical acute angle open to the rotor axis, although of opposing direction, with the plane of symmetry of the hammer heads. This effect may be increased if the lateral flanks of the cylinder segments in the anchored state are disposed in planes radially extending to the rotor axis in the area outside of the hammer heads, with the lateral flanks of adjacent cylinder segments contacting one another.